Age-associated decline in muscle mass and strength impairs functional mobility in older adults. We examined the effects of an eccentric endurance exercise programme (downhill treadmill walking, DTW) at a self-selected walking speed (SSWS) on functional mobility and eccentric and concentric strength of m. quadriceps femoris of older adults. Twenty-four older adults (67±4years) were randomly assigned to complete 3×30min treadmill walks per week for 12weeks on a level (n=11, LTW 0%) or downhill (n=13, DTW -10%) treadmill gradient at SSWS. SSWS was re-adjusted every 4weeks. Participants were assessed for five repetition sit-to-stand (5-RSTS), maximal walking speed (MWS), timed up-and-go (TUG) and dynamic strength. SSWS was similar for both groups with increases from 1.18±0.11 to 1.53±0.09ms(-1) (LTW) and 1.26±0.16 to 1.61±0.12ms(-1) (DTW) (time, P<0.01). Improvements in 5-RSTS, MWS and TUG were substantial and similar for both groups (time, P<0.01). 5-RSTS (baseline LTW: 8.50±1.19s, DTW: 8.54±1.52s) improved by 32 and 34%. MWS (baseline LTW: 2.39±0.38ms(-1), DTW: 2.40±0.33ms(-1)) improved by 22 and 23%. TUG (baseline LTW: 5.58±0.51s, DTW: 5.46±0.89s) improved by 22% for both groups. Peak eccentric and concentric torque did not change. Knee angle of concentric peak torque (180°s(-1)) was decreased after 12weeks in both groups (LTW: 37°±16° to 26°±14°, DTW: 42°±18° to 37°±16°, P<0.05). Regular level and downhill treadmill walking by older adults, at a SSWS, results in substantial improvements in functional mobility. Changes in functional mobility were not explained by changes in dynamic strength of the m. quadriceps femoris.